1. Field of the Invention
The invention is in the field of offset circuits for use, for example, in digital meters employing a dual slope analog-to-digital converter.
2. Description of the Prior Art
Prior art offset circuits have been utilized in digital meters to provide an offset voltage or current to the input of an analog-to-digital converter which is subsequently connected to a display output. These prior art devices generally require complex and expensive additional circuitry, such as a difference amplifier connected for subtracting out or adding a variable offset voltage or current to the input signal which feeds the analog-to-digital converter. Many of these devices have the inherent disadvantages of adversely loading the input impedance of the analog-to-digital converter which preferably has a high input impedance on the order of 100 megohms. High input impedance differential amplifier circuits are expensive, and thus have found only restricted use in offset circuits.